Abstract: Sediment organic matter is one of the important components of lake material cycle. It is of great significance to the environmental protection of lakes to study the characteristics, transportation and transformation of sediment organic matter in lakes. Take Lake Hulun, a typical lake in the Inner Mongolia-Xinjiang lake area located in the cold and arid region of China, as an example, the occurrence characteristics of sediment organic matter in surface sediments, effects of sediment organic matter release and influencing factors were studied using sequential extraction method, three-dimensional fluorescence excitation emission matrix spectrum-parallel factor method (EEMs-PARAFAC), stable carbon isotope (δ¹³C), carbon and nitrogen ratio (C/N), and simulating lab test. The results showed that the content of sediment organic matter in the surface sediments of Lake Hulun was 26.67-38.09 g/kg, and the main component of the sediment organic matter was humin (HM), accounting for 74.1%. The sediment organic matter mainly came from the terrestrial sources, with a relative contribution rate of about 80%. The results of static release simulation test of sediments showed that sediment organic matter release lead to changes in the concentration and composition of dissolved organic matter (DOM) in overlying water. The concentration of dissolved organic carbon (DOC) in overlying water increased from 30.85 mg/L to 37.57 mg/L, and the proportion of humus-like components increased. Sediment organic matter release also resulted in the increase of nitrogen and phosphorus in overlying water. The concentrations of dissolved total nitrogen (DTN) and dissolved total phosphorus (DTP) increased by 0.89 and 0.16 mg/L, respectively. In recent years, the temperature in the Lake Hulun Basin increased, and could enhance the sediment organic matter release. This study showed that although the sediment organic matter in Lake Hulun was mainly composed of refractory components, the release effect of the sediment organic matter on the concentrations of carbon, nitrogen and phosphorus in the water could not be ignored.